Need help/advice big time on 1st gen vf500f tappet screws

Can someone tell how or why the valve tappet adj screws on a 1st gen vf500f can come completely out? We had this happen on 1 of the adjuster screw/nut on 1 of the intake valves on the #2 cyl. We got lucky that time and found both the screw and jam nut before they chewed anything up in the engine. My son and I at first assumed that the jam nut hadn't been tightened when we had put the valve train back together after repairing the CCT but it has happened again not just on the same tappet screw but another 1 on the int valve on the #4 cyl as well and this time I don't think we got so lucky as last time and hurt the motor in the process and we can't be pointing fingers on who didn't tighten the jam nuts because we made for damn sure all nuts were tight after getting lucky on the 1st scare. Can someone tell me WTF is going on? Am I doing something fundamentally wrong? The ONLY thing different I can think of is how we tightened the jam nuts after setting lash. Prior to the CCT repair I always tightened the jam nut once lash was set but being we don't have any special tools I always had a hard time keeping the screw from turning while tightening jam thus messing my lash adjustment up. After the CCT repair I had my son try something different and that is once lash was set, turn the motor over until that particular tappet was opening it's corresponding valve which would put enough pressure on the adjuster screw preventing it from turning while tightening jam nut. Is that where we screwed up or could it be possible that the jam nuts were tight just not tight enough? We never had this problem before the CCT repair. This bike is turning into a money pit and is 1 step away from being parted out unless we can figure out what's going on so any input would be greatly appreciated.

 

It's toast. Took a closer look at it and it dropped an int valve on the #2 cyl due to that rocker arm opening valve 1 too many times without adj screw in place.

 

My son and I talked it over and decided t give this motor 1 last chance and that's provided that
#1- We find both adj screws and nuts and replace them if damaged and cross our fingers that they didn't damage something else in the motor.
#2- We find the valve keepers from the dropped valve and replace if needed.
#3- Make up a tool that I can compress the valve spring to re-install the keepers with compressed air in the cyl keeping the valve closed.
#4- Cross our fingers that int valve isn't bent and or knocked a hole in piston.

I believe the problem was that the jam nuts simply weren't tight enough because I checked a couple others at random and all were hardly tighter than snug and this may be due to the fact on how we tightened them after setting lash which allowed the jam nuts to work loose because my son swears up and down that he had them tighter than that and I believe him. We'll keep all informed on how it works out, in the mean time wish us luck.

 

well worst case scenario, you might be able to find another engine, or the necessary parts to rebuild your engine somewhere on eBay...

good luck getting your bike back on the road!

 

It's quite unfortunite, but it's the nature of these particular beasts (the 1st gens)

Good luck with the rebuild, and make sure when it's buttoned up and running you keep the revs low.

 

Yeah I think we're pissing in the wind on this one because it really depends on whether the intake valve is still intact and to be honest, I've never seen a dropped valve that didn't beat itself to death. First thing will be seeing how high the valve stem comes up, if it stops either higher or lower than the other intake valve next to it, then we'll know it's hurt bad. If by chance it stops at the same height then compressed air in the cyl and it's ability to keep the valve closed will determine it's fate. Long shot I know but being the only cost involved will be my time I think it's worth a shot to find out. I did spot another 85 vf500f motor on ebay for $250 ($500 with shipping included) but it's in Illinois so I could cut the shipping cost by picking it up myself however my son is so frustrated with the bike right now he just wants it to go away and get another more modern bike. This wasn't the first time my son set the valve lash on this motor and up until now the lash adj screws never worked themselves loose and I can't see how our change in how he tightened the jam nuts would have any effect. The only thing I can think of is maybe the threads in the jam nuts were getting weak so even though they felt tight, they weren't strong enough to stay tight.

 

Hope all works out.

Don't get frustrated but do get the Factory tools for adjusting the tappets.







Use a torque wrench, as a double check, in conjunction with the Factory tools to properly secure the nut and you'll be in high cotton.

Good luck!

 

Not looking good so far. I pulled the cams and the retainer from the valve in question and lo and behold the keepers were still setting in the retainer (not making this up) and from a strictly visual point of view with the retainer and spring removed the valve stem stopped at the same height as the int valve next to it however when I applied compressed air to the cyl, I could hear that compressed air coming out of the carb telling me the face of the valve is beat up and not sealing. My son owns the bike so it'll be up to him on whether he wants to dig deeper as in pulling the cyl head.

 

This engine keeps getting luckier by the minute because my son has decided to go another step further and pull the head so now it depends on how much of a beating the cyl head took as well as the piston. Let you know what we find later.

 

Good condition, used heads do show up on eBay (with no visible valve train wear) now and again.

I think this is in part based a 500 being purchased new, enjoyed for a season or two and then sitting due to the carbs needing to be cleaned or the like. Add 25 years of storage in the back of the tool shed, these bikes are then parted out.

If the piston is okay, a used low milage head may be a good way to go.

Good luck!

 

Got the front cyl head off and it seems fine and so does the top of the piston. The valve itself had no visual damage until I chucked it up in my lathe to spin it and sure enough there is a slight wobble on the face/head of the valve meaning it did kiss the piston just enough to bend it and ruin it's ability to seal. I've been doing some parts searching and I think a new int valve is still available, I even found 1 on ebay but it's for an '86 and I don't know if it will work on our '85 cyl head. The biggest issue is finding new head gaskets. I checked out "copper gaskets unlimited" but the info I need to know is what thickness of gasket will I need so if any of you know what the crushed thickness of an OEM vf500f head gasket is, let me know because my factory manual isn't telling me.

 

I did spot 1 on ebay for $50 but so far it seems all ours needs is an int valve but thanks for the tip anyhow and thanks for the tip on the "special" tools needed for lash adj.

 

IIRC, valves and valve springs are different on the '86.

Do not use copper head gaskets, these are a no go on the 500.

Glad to hear the piston is okay.

 

Thanks for the tip on copper gaskets. I just need to make sure that current gasket sets include the head gaskets as well even when an ad says "complete gasket set".

 

More info on head gaskets can be found here:

http://vfrworld.com/forums/1st-2nd-generation-1983-1989/31074-scan-em-if-you-got-em-vf500f-head-gasket-patterns.html

 

I'll be replacing the 2 intake valves where the adj screw fell out because under closer inspection of the dropped valve I noticed at the top of the valve where the keepers lock onto the stem its evident that the groove on the stem is severely worn from the rocker arm opening the valve by pushing on the retainer first, loosening the keepers just a bit then getting snapped tight over and over again. I took the valve in question, slid the retainer on it then the keepers and right when the keepers should have locked onto the valve stem I was able to push the stem all the way through with just the force of my finger pushing on it. I would post a pic of the wear I'm talking about but couldn't get my camera to take a clear pic of it. Once I spotted that I looked at the other int valve that lost it's adj screw and sure enough I could see it's keepers were working themselves loose as well. I'm just glad I spotted it now because I would've been thoroughly pissed if we replaced just the bent valve, got it all back together only to drop the other valve because we assumed it was OK. In the meantime I'm going to post on the want ad part of this site to see if any of you guys have a spare couple of intake valves.

 

Glad you caught this.

If you are not able to find OEM valves, KPMI should be able to help with supplying a match to OEM.

Good luck and keep us posted.

 

I've got my eye on a cyl head on ebay but right now the biggest concern is finding the missing adj screws and jam nut so my son will be busy today dropping the pan to see if we can spot them and crossing our fingers that nothing else in the motor got beat up by the screws. So far we've got the keepers from the dropped valve and 1 jam nut accounted for so my son needs to find the 2 screws and 1 jam nut. I just hope we don't have to tear the whole motor down to find them all.

 

If I could suggest, while you have the oil pan off, this is a good time to inspect the screen for the oil pump.

Keep us posted. Hope all goes well.

 

It's toast. We found the 2 adjuster screws and jam nut in the pan but found something else that we didn't want to find and that was a small piece of aluminum. Closer look underneath and the piece came from above oil pump. All we had to do to remove the oil pump was remove the bolt that attaches the pump shaft to the drive sprocket inside right side cover and the pump literally fell out and the following pic will show why. Only way to fix that is to get another set of engine cases. Right now my son is posting the bike to part it out and it does have a lot of new parts so take a look.